TW202016027A - Water treatment method and water treatment device - Google Patents

Abstract

An object of the invention is to provide a water treatment method and water treatment device which enable fast and stable biological treatment of water that contains ammoniacal nitrogen, even when the water to be treated has a high nitrogen content. A water treatment device 1 (water treatment method) of the invention biologically treats water containing ammoniacal nitrogen, and comprises a nitrification device 10 (nitrification step) which oxidizes ammoniacal nitrogen to nitrous acid or nitrate nitrogen using nitrifying bacteria including nitrous acid oxidizing bacteria and autotrophic ammonia oxidizing bacteria contained in microbial activated sludge, and a nitrification speed control device which performs control so as to ensure the existence of a molybdenum compound in the nitrification device 10 in an amount sufficient to provide the water being treated with a molybdenum concentration of at least 0.025 mgMo/gN, and so as to produce a nitrification speed for the sludge of at least 0.11 [kgN/(kgVss·day)].

Description

Water treatment method and water treatment device

The invention relates to a water treatment method and water treatment device for biologically oxidizing and reducing ammonia nitrogen contained in water to be treated to nitrogen gas.

The nitrogen component contained in the drainage is one of the causes of eutrophication of lakes and marshes or enclosed sea areas. Therefore, especially when the drainage contains a high concentration of nitrogen components, it must be removed in the drainage treatment step. Generally speaking, biological treatment using microbial activated sludge is mostly used, for example, in the treated water containing ammonia nitrogen, nitrification and denitrification treatment is carried out by the following two steps: nitrification step, under aerobic conditions, the ammonia nitrogen Oxidation to nitrous acid or nitrate nitrogen; and denitrification step, under anaerobic conditions, in the presence of hydrogen donor, reduce nitrous acid, nitrate nitrogen to nitrogen. In addition, when the treated water contains a large amount of organic matter, there are also cases where the treatment is carried out by the following circulating nitrification denitrification method: the treated water is supplied to the denitrification tank, and the nitrification tank contains nitrous acid, The mixed liquid of nitrate nitrogen is circulated to the denitrification tank, and the organic matter in the treated water is used as a hydrogen donor to denitrify.

In any treatment method, the nitrifying bacteria and denitrifying bacteria in the microbial activated sludge are used, but the denitrifying bacteria can assimilate heterotrophic bacteria of organic matter. In contrast, the nitrifying bacteria are self-operated with inorganic carbon as the carbon source Sex bacteria, so the reproduction rate is very slow compared to denitrifying bacteria. In the case of a treatment method using microbial activated sludge, since the activated sludge is mixed with nitrifying bacteria and denitrifying bacteria, the proportion of nitrifying bacteria in the sludge can be said to be very small. For the treatment of nitrogen-containing wastewater using the nitrification denitrification method, the key factor for the removal efficiency of nitrogen in the wastewater is the activity of the nitrifying bacteria in the nitrification step. In addition, nitrifying bacteria are strongly affected by the water temperature, and lowering the water temperature may cause a significant decrease in activity. Therefore, in order not to deteriorate the quality of the treated water, it is necessary to make the nitrification rate (ammonia oxidation specific activity) per unit of sludge in the nitrification step lower than in the nitrogen removal step. For example, Non-Patent Document 1 reports that the specific activity of ammonia oxidation is 0.113 mgN/(mgVSS·day) and the specific activity of nitrous acid oxidation is 0.056 mgN/(mgVSS·day). In actual treatment, under the condition of a water temperature of 20°C, the volume load of the nitrification tank is usually set by operating at a treatment rate of sludge per unit of 0.05 to 0.1 kgN/(kgVSS·day).

On the other hand, in the case of treating the treated water containing high-concentration nitrogen, such as the nitrogen concentration of the treated water, for example, the microorganism concentration activated sludge containing nitrifying bacteria and denitrifying bacteria, for example, a nitrification step In the case of reduced nitrification activity. If the nitrification activity decreases, the final treatment water quality also deteriorates, so it is necessary to set the nitrification rate per unit of sludge in the nitrification step to be lower than the above 0.05 to 0.1 kgN/(kgMLVSS·day). As a result, it is difficult to maintain the treatment rate at High speed situation. [Conventional Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2006-272287 [Non-patent literature]

Non-Patent Document 1: Araki et al. (1999), FISH method for quantification and spatial distribution analysis of nitrifying bacteria in biofilms; Journal of Water Environment, Vol. 22, No. 2, pp.152-159 Non-Patent Literature 2: Microbiology nitrate respiration-Genes, enzymes, and environmental distribution, Journal of Biotechnology, 155(2011), pp. 104-117 Non-Patent Document 3: Molybdenum as a micronutrient for Nitrobacter, Journal of Bacteriology, 89 (1965), pp. 123-128 Non-Patent Document 4: Molecular analysis of ammonia oxidation and denitrification in natural environments, FEMS Microbiology Reviews, 24(2000), pp.673-690

[Problems to be Solved by the Invention]

An object of the present invention is to provide a water treatment method and a water treatment device, in biological treatment of treated water containing ammoniacal nitrogen, even if the nitrogen concentration in the treated water is high, it can be stably treated at a rapid treatment rate. [Technical means to solve the problem]

The present invention is a water treatment method that biologically treats treated water containing ammoniacal nitrogen; the method includes a nitrification step: by self-supporting ammonia oxidizing bacteria and nitrite oxidizing bacteria contained in microbial activated sludge Nitrifying bacteria, oxidize the ammonia nitrogen to nitrous acid or nitrate nitrogen; in the nitrification step, the molybdenum compound is present in the treated water so that the molybdenum concentration becomes 0.025 mgMo/gN or more; per unit of sludge The nitrification rate is above 0.11 [kgN/(kgVSS·day)].

In this water treatment method, the molybdenum concentration in the nitrification step is preferably 2 mgMo/L or less relative to the water to be treated.

In this water treatment method, the nitrogen concentration in the water to be treated is preferably 100 mgN/L or more.

In the water treatment method, it is preferable to further include a denitrification step: by denitrifying bacteria contained in the microbial activated sludge, the nitrous acid or nitrate nitrogen produced in the nitrification step is reduced to nitrogen.

In the denitrification step of the water treatment method, it is preferable to give a time variation to the amount of addition of the hydrogen donor so that the difference between the maximum concentration and the minimum concentration of the hydrogen donor in the hydraulic retention time of the treated water becomes 50 mgTOC/ Above L, the microbial activated sludge containing the nitrifying bacteria and denitrifying bacteria is granulated.

In the water treatment method, the denitrification step preferably includes at least a first denitrification step and a second denitrification step; in the denitrification step, a hydrogen donor is supplied at least in the first denitrification step so that The difference between the maximum concentration of the hydrogen donor of the first denitrification step and the minimum concentration of the hydrogen donor of the second denitrification step in the hydraulic retention time of the treated water of the second denitrification step becomes 50 mgTOC/L or more .

The present invention is a water treatment device that biologically treats water to be treated that contains ammoniacal nitrogen, and includes: nitrification means for nitrifying bacteria containing self-supporting ammonia oxidizing bacteria and nitrite oxidizing bacteria contained in microbial activated sludge , Oxidizing the ammonia nitrogen to nitrous acid or nitrate nitrogen; and a nitrification rate control means for performing the following control: in the nitrification means, the molybdenum concentration of the treated water is 0.025 mgMo/gN or more The molybdenum compound is allowed to exist, and the nitrification rate per unit sludge is 0.11 [kgN/(kgVSS·day)] or more.

In the water treatment device, the nitrification rate control means preferably controls the molybdenum concentration in the nitrification means to be 2 mgMo/L or less relative to the water to be treated.

In the water treatment device, the molybdenum concentration in the water to be treated is preferably 0.0001 mgMo/L or less.

In the water treatment device, the nitrogen concentration in the water to be treated is preferably 100 mgN/L or more.

In the water treatment device, it is preferable to further include a denitrification means: by denitrifying bacteria contained in the microbial activated sludge, the nitrous acid or nitrate nitrogen produced by the nitrification means is reduced to nitrogen.

In the water treatment apparatus, it is preferable to further include a hydrogen donor concentration control means for performing the following control: in the denitrification means, the amount of addition of the hydrogen donor is given a time change so that the hydraulic retention time of the treated water is within The difference between the maximum concentration and the minimum concentration of the hydrogen donor becomes 50 mgTOC/L or more, thereby granulating the microbial activated sludge containing the nitrifying bacteria and denitrifying bacteria.

In the water treatment device, the denitrification means preferably includes at least a first denitrification means and a second denitrification means; the hydrogen donor concentration control means performs the following control: in the denitrification means, at least the The hydrogen donor is supplied in the first denitrification means so that the maximum concentration of the hydrogen donor of the first denitrification means and the hydrogen of the second denitrification means in the hydraulic residence time of the treated water of the second denitrification means The difference in the minimum concentration of the donor becomes 50 mgTOC/L or more. [Effect of the invention]

According to the present invention, in the biological treatment of the treated water containing ammoniacal nitrogen, even if the nitrogen concentration in the treated water is high, the treatment can be stabilized at a rapid treatment rate.

The embodiments of the present invention will be described below. This embodiment is an example of implementing the present invention, but the present invention is not limited to this embodiment.

FIG. 1 shows an outline of an example of a water treatment device according to an embodiment of the present invention, and its structure will be described.

The water treatment device 1 is a water treatment device that biologically treats treated water containing ammoniacal nitrogen, and includes a nitrification device 10 as a means of nitrification, which includes self-supporting ammonia-oxidizing bacteria contained in microbial activated sludge Nitrifying bacteria with nitrite oxidizing bacteria to oxidize ammonia nitrogen to nitrous acid or nitrate nitrogen; and nitrification speed control means to perform the following control: in the nitrification device 10, the water to be treated so that the molybdenum concentration becomes 0.025 The method above mgMo/gN makes molybdenum compound exist and makes the nitrification rate per unit of sludge The degree becomes 0.11 [kgN/(kgVSS·day)] or more. The water treatment device 1 may further include a denitrification device 12 as a denitrification means to reduce nitrous acid or nitrate nitrogen generated in the nitrification device 10 to nitrogen gas by denitrification bacteria contained in the microorganism activated sludge.

The water treatment device 1 may further include: a solid-liquid separation device 14 that separates the treated water from the microbial activated sludge as solid-liquid separation means to obtain treated water; and a sludge return piping 24 that uses the solid-liquid separation device as a return means The sludge separated by 14 is returned to the solid-liquid separation device 14 in the previous stage. In addition, the water treatment device 1 may include a treated water adjustment tank 15 that stores treated water.

In the water treatment device 1 of FIG. 1, the outlet of the treatment water adjustment tank 15 and the inlet of the nitrification device 10 are connected through a pipe 16 via a treatment water supply pump 17 as a treatment water supply amount adjustment means; The outlet of the nitrification device 10 and the inlet of the denitrification device 12 are connected by a pipe 18; the outlet of the denitrification device 12 and the inlet of the solid-liquid separation device 14 are connected by a pipe 20; The treated water outlet is connected to the pipe 22; the sludge outlet of the solid-liquid separation device 14 and the pipe 16 are connected via the sludge return pipe 24 via the sludge return pump 25. In the piping 16, on the downstream side of the treated water supply pump 17, a flow rate measuring device 19 is provided as a method for measuring the flow rate of the treated water for measuring the flow rate of the treated water; on the downstream side of the flow rate measuring device 19, the sludge return piping 24, on the upstream side of the connection point, is connected to a molybdenum compound supply pipe 26 via a molybdenum compound supply pump 21 as a means for adjusting the supply of molybdenum compound; The donor supply pump 23 is connected to the hydrogen donor supply pipe 28.

The water treatment method and the operation of the water treatment device 1 of this embodiment will be described.

The to-be-treated water containing ammonia nitrogen is supplied to the to-be-treated water supply pump 17 from the to-be-treated water adjustment tank 15, and the liquid is sent to the nitrification apparatus 10 through the piping 16. In the nitrification device 10, the ammonia nitrogen contained in the treated water is oxidized to nitrous acid or nitrate nitrogen by the nitrifying bacteria contained in the self-supporting ammonia oxidizing bacteria and nitrite oxidizing bacteria contained in the microbial activated sludge (Nitrification step). Here, in the piping 16, the molybdenum compound is supplied to the water to be treated through the molybdenum compound supply pump 21 through the molybdenum compound supply pump 26, so that the molybdenum compound is present so that the molybdenum concentration becomes 0.025 mgMo/gN or more (molybdenum compound supply step). The nitrification liquid is sent to the denitrification device 12 through the pipe 18.

In the denitrification device 12, the hydrogen donor is supplied by the hydrogen donor supply pump 23, and the hydrogen donor is supplied via the hydrogen donor supply piping 28. The heterogenous denitrifying bacteria contained in the microbial activated sludge will be used in the nitrification device 10. (Nitrification step) The nitrous acid or nitrate nitrogen produced is reduced to nitrogen (denitrification step). The nitrogen removal liquid is sent to the solid-liquid separation device 14 through the pipe 20.

In the solid-liquid separation device 14, the treated water is separated from the microbial activated sludge of the denitrification liquid to obtain treated water (solid-liquid separation step). The treated water obtained by solid-liquid separation is discharged through the pipe 22. On the other hand, at least a part of the sludge obtained by the solid-liquid separation is sent back to the pipe 16 through the sludge return pipe 24 by the sludge return pump 25 and mixed with the water to be treated. The sludge may be sent back to the solid-liquid separation device 14 (solid-liquid separation step) before, for example, it may be sent back to the nitrification device 10, the denitrification device 12, or the pipes 18, 20. At least a part of the sludge obtained by the solid-liquid separation can be discharged from the solid-liquid separation device 14 to the outside of the system.

The inventors of the present invention found that the use of microbial activated sludge containing nitrifying bacteria containing self-supporting ammonia oxidizing bacteria and nitrite oxidizing bacteria to treat nitrogen-containing treated water containing ammoniacal nitrogen, especially the nitrogen concentration of the treated water For example, in the method of high-concentration nitrogen-containing treated water of 100 mgN/L or more, in the case where the metabolic activity of microorganisms is reduced and the treatment rate is reduced, the molybdenum concentration of the treated water is made 0.025 mgMo/gN or more In this way, molybdenum compounds are present, and the nitrification rate per unit of sludge is controlled to be above 0.11 [kgN/(kgVSS·day)], so that the metabolic activity of nitrifying bacteria is greatly restored, further improved, and a stable and fast processing speed can be obtained . In addition, the inventors of the present invention found that the treatment of nitrogen-containing quilt containing ammoniacal nitrogen was carried out by using microbial activated sludge containing nitrifying bacteria containing self-supporting ammonia oxidizing bacteria and nitrite oxidizing bacteria, and heterogeneous denitrifying bacteria. In the method of treating water, especially high-concentration nitrogen-containing treated water with a nitrogen concentration of, for example, 100 mgN/L or more in the treated water, when the metabolic activity of microorganisms is reduced and the treatment speed is reduced, by treating the treated water , The molybdenum compound is present in such a way that the molybdenum concentration becomes 0.025 mgMo/gN or more, and the nitrification rate per unit sludge is controlled to 0.11 [kgN/(kgVSS·day)] or more, so that the nitrifying bacteria and denitrifying bacteria The metabolic activity is greatly restored and further improved, and a stable and fast processing speed can be obtained.

In biological treatment of nitrogen-containing treated water, especially high-concentration nitrogen-containing treated water, by using molybdenum compounds, the activity of nitrifying bacteria including ammonia oxidizing bacteria and nitrite oxidizing bacteria in microbial activated sludge is improved. The nitrogen concentration in the water to be treated is high, and it can still be treated stably at a rapid treatment rate. In addition, in the biological treatment of nitrogen-containing treated water, especially high-concentration nitrogen-containing treated water, the use of molybdenum compounds not only improves the activity of denitrifying bacteria in microbial activated sludge, but also improves The activity of nitrifying bacteria of nitrate oxidizing bacteria, so even if the concentration of nitrogen in the water to be treated is high, it can still be treated stably at a rapid treatment rate.

The nitrification rate per unit sludge should be controlled to be above 0.11 [kgN/(kgVSS·day)], and should be controlled below 0.24 [kgN/(kgVSS·day)]. If the nitrification rate per unit sludge is less than 0.11 [kgN/(kgVSS·day)], the effect of adding molybdenum is not obvious. In addition, if the nitrification rate per unit of sludge exceeds 0.24 [kgN/(kgVSS·day)], ammonia nitrogen remains in the nitrification tank. Depending on the pH, the ammonia concentration in the tank may cause ammonia oxidizing bacteria or The activity of nitrite oxidizing bacteria is reduced, and the processing performance is deteriorated.

The nitrification rate per unit of sludge is based on the treatment capacity ((ammonia nitrogen concentration of treated water-ammonia nitrogen concentration of treated water [mg/L]) × flow rate [m ³ /day]), and the amount of sludge in the tank (MLSS [mg/L] × water tank volume [m ³ ]) is determined. The ammonia nitrogen concentration of the treated water, the ammonia nitrogen concentration of the treated water, and the sludge concentration in the nitrification device 10 are measured, and the flow rate of the treated water supply pump 17 is adjusted so as to be a predetermined treatment rate per unit of sludge. In addition, the control of the amount of molybdenum added to the amount of ammonia nitrogen flowing in may be implemented by the molybdenum compound supply pump 21. In this case, the treated water supply pump 17, the flow rate measuring device 19, and the molybdenum compound supply pump 21 function as a nitrification speed control means for performing the following control: in the nitrification device 10, the treated water is adjusted so that the molybdenum concentration The molybdenum compound is present so that it becomes 0.025 mgMo/gN or more, and the nitrification rate per unit sludge becomes 0.11 [kgN/(kgVSS·day)] or more. The treated water supply pump 17, the flow rate measuring device 19, and the molybdenum compound supply pump 21 can be connected to the control device by electrical connection or the like to perform automatic control.

In general, in the case of performing biological treatment of drainage, in order to maintain the reproduction and metabolic reaction of microorganisms, it is necessary to maintain a nutrient balance in the treated water. As nutrients for cell constituents, carbon (C), oxygen (O), nitrogen (N), hydrogen (H), and phosphorus (P) called "biophilic elements" become essential components. Others, compared to the demand for biophilic elements is less, but sulfur (S), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), chlorine (Cl), iron (Fe), as Cell components are also essential components, so when the content of various elements in the water to be treated is small, it is advisable to supplement them with other substances. On the other hand, there is less demand, but trace elements that participate in the microbial enzyme metabolism are also better. Examples include fluorine (F), silicon (Si), vanadium (V), chromium (Cr), and manganese (Mn). , Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Arsenic (As), Selenium (Se), Molybdenum (Mo), Iodine (I), etc. However, the demand for these trace elements containing heavy metals is very small. It is assumed that there is a sufficient amount of water required in the treated water, so it is generally not added from the outside to the treated water or the treatment system. On the other hand, when the wastewater discharged from factories using ultrapure water in the semiconductor industry and the like is biologically treated, assuming that trace elements such as the above are insufficient, there are mixed water, industrial water, well water, etc. The situation in which the treated water is used for replenishment. However, in the case where the nitrogen concentration in the treated water is high (for example, 100 mgN/L or more), the nitrification rate may decrease. Even in this state, the water treatment method and water treatment device of the present embodiment can stabilize the treatment and perform high-speed treatment by supplying a predetermined amount of molybdenum compound into the treatment system.

Regarding the treatment of the nitrogen component in the treated water, the reactions are mainly divided into the following reactions: 1. NH ₄ ⁺ →NO ₂ ^－ (ammonia oxidizing bacteria) 2, NO ₂ ^－ →NO ₃ ^－ (nitrite oxidizing bacteria) 3. NO ₃ ^－ →N ₂ (denitrifying bacteria)

Regarding the denitrification bacteria, the reduction reaction of nitric acid dissociation under anaerobic conditions (nitric acid respiration) is undergoing a biochemical review. For example, according to Non-Patent Document 2, the reaction from nitric acid to nitrogen is clearly divided into [NO ₃ ^－ →NO ₂ ^－ →NO→N ₂ O→N ₂ ], and catalyzes the reduction of [NO ₃ ^－ →NO ₂ ^－ ] The reaction enzyme, molybdenum element is involved. That is, regarding the denitrification reaction in the wastewater treatment system, although the extent of the necessary amount is not yet known, it is assumed that the activity is improved by adding a molybdenum compound.

In addition, through research, it was clarified that molybdenum is required when nitrite oxidizing bacteria oxidize nitrite. For example, Non-Patent Document 3, a review of nitrite-oxidizing bacteria culture Nitrobacter of conditions i.e., by adding at least the display 10 ^{- 9} M of molybdenum, and the use of cells for the propagation of Nitrobacter nitrite increased 11 times. That is, regarding the oxidation reaction of nitrous acid in the wastewater treatment system, it is assumed that the activity is improved by adding a molybdenum compound.

On the other hand, as enzymes involved in ammonia oxidation metabolism of ammonia oxidizing bacteria, two types of ammonium monooxygenase (AMO) that oxidizes ammonia to produce hydroxylamine, and hydroxylamine oxidoreductase (HAO) that further produces nitrous acid from the generated hydroxylamine Enzymes are involved, but they are not reports of enzyme reactions in which molybdenum is involved (see Non-Patent Document 4).

Patent Document 1 describes a method of coexisting cobalt and water to be treated and further coexisting molybdenum, calcium, and magnesium components in order to efficiently advance the nitrification reaction. In the example of Patent Document 1, the nitrification and denitrification treatment test of the lower concentration treated water with a nitrogen concentration of 70 mgN/L was verified under the coexistence of molybdenum concentration of 1 mgMo/L (14.3 mgMo/gN). Under the condition of a load of 2.5 gN/(kgMLSS·hour) [=0.06 kgN/(kgMLSS·day)], the nitrogen removal rate is 90%, but it is difficult to think that it has a significant effect.

The inventors of the present invention have found that in the method of treating microbial activated sludge coexisting with ammonia oxidizing bacteria and nitrite oxidizing bacteria, especially the treated water containing high concentration of nitrogen, by supplying a certain amount of molybdenum, not only can the sub The nitric acid oxidation reaction also greatly improves the activity of ammonia-oxidizing bacteria. In addition, the inventors of the present invention have found that the use of microbial activated sludge coexisting with various bacteria containing ammonia oxidizing bacteria, nitrous acid oxidizing bacteria, and denitrifying bacteria to treat especially treated water containing high concentration of nitrogen In the method, by supplying a certain amount of molybdenum, not only can the nitrite oxidation or denitrification (nitric acid reduction) reaction be improved, but also the activity of ammonia oxidizing bacteria can be greatly improved. The microbial activated sludge coexisting with self-supporting bacteria such as ammonia oxidizing bacteria and nitrite oxidizing bacteria, and denitrifying bacteria that can assimilate organic matter, including the denitrifying bacteria that reproduce faster than nitrifying bacteria. Sexual bacteria dominate the sludge. Generally speaking, it is assumed that the metabolic reactions of each bacterium are independent, but in the microbial activated sludge where a plurality of functional microorganisms exist, each bacterium is in a coexisting relationship. The mechanism by which the addition of molybdenum compounds improves the ammonia oxidation activity is not yet known, but the supply of molybdenum can increase the metabolic activity of denitrifying bacteria and other foreign bacteria, so it is speculated that the supply of molybdenum also improves the activity of ammonia oxidation There are links.

In the present embodiment, the water to be treated is nitrogen-containing water containing ammonia nitrogen, especially nitrogen-containing water containing high-concentration ammonia nitrogen, and may further contain organic nitrogen. Examples of the water to be treated include industrial wastewater such as electronic industrial wastewater, metal refining factory wastewater, and power plant wastewater, or wastewater including digestion and separation water discharged during sludge treatment. Here, the drainage of the electronics industry includes various kinds of medicines. In addition, the components in the drainage vary greatly depending on the manufactured product. As the nitrogen-containing water, for example, wafer cleaning drainage can be cited. In addition to ammonia, the drainage contains tetramethylammonium hydroxide (TMAH), hydrogen peroxide, fluoride ions, isopropyl alcohol (IPA), etc.

The concentration of molybdenum in the water to be treated is, for example, 0.0001 mgMo/L or less. In addition, the nitrogen concentration in the water to be treated is preferably 100 mgN/L or more, and more preferably 400 mgN/L or more, which is suitable for applying the water treatment method and water treatment apparatus of this embodiment.

When such nitrogen-containing water is biologically treated, blocking substances such as hydrogen peroxide or fluoride ions have a blocking effect on organisms, so it is preferable to remove them in advance. Existing techniques can be used as the treatment method of these obstructive substances. For example, in the treatment of hydrogen peroxide, a method of adding an enzyme, a method of injecting a reducing agent, a method of contacting with activated carbon, etc. may be mentioned. In addition, in the treatment of fluoride ions, a method of adding calcium to make calcium fluoride and removing it, a method of treating with an ion exchange resin, etc. may be mentioned.

It is advisable to store the nitrogen-containing water that removes obstructive substances such as hydrogen peroxide or fluoride ions in the water tank before performing the treatment in the biological treatment step, to stabilize the flow rate and water quality in the biological treatment step, and to use alkali or A pH adjusting agent such as an acid is adjusted to an appropriate pH (for example, pH 6.5 to 8.0). Then, the nitrogen-containing water (processed water) whose flow rate, water quality, pH, etc. are adjusted is sent to the biological treatment step.

The nitrification step in the nitrification device 10 is to supply the treated water to the nitrification section (for example, a nitrification tank), and oxidize the ammonia nitrogen such as ammonium ions in the treated water to nitrous acid in an aerobic manner (for example, in the presence of oxygen) Or the step of nitrate nitrogen. The nitrification section is connected to, for example, an air introduction pipe, and has a structure capable of supplying oxygen-containing gas such as air to the water to be treated in the nitrification section. Then, in the nitrification section, by the action of nitrifying bacteria, ammonia nitrogen such as ammonium ions in the treated water is nitrified into nitrous acid or nitrate nitrogen. Here, nitrifying bacteria refer to the generic term of self-supporting ammonia oxidizing bacteria that oxidizes ammoniacal nitrogen such as ammonium ions to nitrite ions, and self-supporting nitrite oxidizing bacteria that oxidizes nitrite ions to nitrate ions.

When the molybdenum contained in the water to be treated is insufficient, the molybdenum compound may be added externally. A molybdenum compound, for example, as a molybdenum compound solution, is supplied to the water to be treated through the molybdenum compound supply pipe 26, and the molybdenum compound is mixed with the water to be treated and supplied into the system. The molybdenum compound may be supplied in proportion to the amount of nitrogen to be treated. By supplying a certain amount of molybdenum compound, the activity of nitrifying bacteria (ammonia oxidizing bacteria and nitrite oxidizing bacteria) and denitrifying bacteria can be maintained at a high level, and it can be operated stably or processed at high speed.

Examples of the molybdenum compound include molybdic acid compounds such as sodium molybdate, potassium molybdate, and ammonium molybdate. The form of the molybdenum compound is not particularly limited. For example, if it is in a solution state, the bacteria in the microbial activated sludge can be easily utilized. For example, it is preferable to prepare an aqueous solution of sodium molybdate or potassium molybdate in advance and add it.

The addition point of the molybdenum compound may be supplied to the piping 16 before the nitrification treatment, or may be supplied to the nitrification device 10 that mixes the water to be treated with the microorganism activated sludge. In addition, if it is considered that the added molybdenum compound is returned as the returned sludge to a stage earlier than the solid-liquid separation step and circulated in the system, a molybdenum compound supply pipe may be connected to the pipe 18 or the denitrification device 12 to supply the molybdenum compound.

In the nitrification apparatus 10 (nitrification step), the molybdenum compound is present in the water to be treated so that the molybdenum concentration becomes 0.025 mgMo/gN or more, and the molybdenum compound is preferably present so that the molybdenum concentration becomes 0.1 mgMo/gN or more. The upper limit of the molybdenum concentration is not particularly limited, and it is, for example, 0.25 mgMo/gN or less. In the nitrification device 10 (nitrification step), if the molybdenum concentration is less than 0.025 mgMo/gN with respect to the water to be treated, the activity of nitrifying bacteria (ammonia oxidizing bacteria and nitrite oxidizing bacteria) and denitrifying bacteria is not maintained. The effect of the situation.

In the nitrification device 10 (nitrification step), the molybdenum concentration is preferably 2 mgMo/L or less relative to the water to be treated. If the concentration of molybdenum exceeds 2 mgMo/L with respect to the water to be treated, the nitrification reaction may be hindered.

A carrier carrying microorganisms can be set in the nitrification section. Although the carrier for supporting microorganisms is not particularly limited, for example, a carrier made of resin such as plastic or polyurethane is preferably used.

The denitrification step in the denitrification device 12 is, for example, to supply a hydrogen donor to a completely mixed denitrification section (such as a denitrification tank) to reduce nitrous acid or nitrate nitrogen generated in the nitrification section under oxygen-free conditions Steps to nitrogen. In the denitrification section (for example, a denitrification tank), nitrous acid or nitrate nitrogen is reduced to nitrogen by the action of heterotrophic bacteria, that is, denitrification bacteria. In the denitrification section, in order to carry out the treatment efficiently, it is advisable to provide a stirring device for mixing the nitrification liquid and the microbial activated sludge under the anaerobic condition.

A carrier carrying microorganisms can be provided in the denitrification section. Although the carrier for supporting microorganisms is not particularly limited, it is preferable to use a carrier made of resin such as plastic or polyurethane.

The hydrogen donor for denitrification used in this embodiment includes, for example, alcohols such as methanol, ethanol, and isopropanol; organic acids such as acetic acid; hydrogen; acetone; glucose; methyl ethyl ketone; tetramethyl hydroxide One or more kinds of ammonium (TMAH), etc., but not limited to them, etc. As a hydrogen donor, all known in the past can be used. As a hydrogen donor, organic substances contained in the water to be treated can also be used.

The solid-liquid separation step in the solid-liquid separation device 14 is to separate the nitrogen component by the nitrifying bacteria and denitrifying bacteria in the microbial activated sludge into nitrification and denitrification denitrification liquid into treated water and microbial activated sludge , And get the step of treating water.

The solid-liquid separation device 14 is not particularly limited, but examples include separation devices such as sedimentation separation, pressurized floatation, filtration, and membrane separation. In the solid-liquid separation step, the treated water is obtained, and the separated microbial activated sludge is also obtained. Part of the microbial activated sludge is extracted as excess sludge out of the system, and part of it is returned to, for example, the nitrification device 10 (nitrification step), thereby maintaining the system The amount of microbial activated sludge.

If a hydrogen donor is added to the denitrification device 12, but there is a concern that the hydrogen donor will remain after the denitrification treatment, the treatment water quality may be deteriorated. The denitrification device 12 (denitrification step) and the solid-liquid separation device 14 (solid-liquid separation Between steps), an oxidation device is set up, which acts as an oxidation means to treat the hydrogen donor in an aerobic manner.

An example of these forms of water treatment equipment is shown in FIG. 2. In the water treatment device 3 of FIG. 2, an oxidation device 30 is provided between the denitrification device 12 (denitrification step) and the solid-liquid separation device 14 (solid-liquid separation step). The outlet of the denitrification device 12 and the inlet of the oxidation device 30 are connected by a pipe 32; the outlet of the oxidation device 30 and the inlet of the solid-liquid separation device 14 are connected by a pipe 34.

The denitrification liquid obtained in the denitrification device 12 (denitrification step) is sent to the oxidation device 30 through the pipe 32. In the oxidation step in the oxidation device 30, the hydrogen donor is treated in an aerobic manner in an oxidation section (for example, an oxidation tank). The oxidizing section (for example, an oxidizing tank) is connected to the air introduction pipe in the same manner as the nitrification section, for example, and has a structure that can supply oxygen-containing gas such as air to the water to be treated in the oxidizing section.

The oxidation treatment liquid oxidized in the oxidation device 30 is sent to the solid-liquid separation device 14 through the piping 34, and thereafter, the treatment is performed in the same manner as the water treatment device 1 in FIG.

In the case where the water to be treated contains organic matter and nitrogen, the hydrogen donor for the denitrification reaction may not be added from the outside, and the organic matter in the water to be treated as a hydrogen donor may cause a denitrification reaction.

An example of these forms of water treatment equipment is shown in FIG. 3. In the water treatment device 5 of FIG. 3, the outlet of the treated water adjustment tank 15 and the inlet of the denitrification device 12 are connected via a pipe 36 through the treated water supply pump 17; the outlet of the denitrification device 12 and nitrification The inlet of the device 10 is connected by a pipe 38; the outlet of the nitrification device 10 and the inlet of the solid-liquid separation device 14 are connected by a pipe 40; the treated water outlet of the solid-liquid separation device 14 is connected to a pipe 42; The sludge outlet of the solid-liquid separation device 14 and the pipe 36 are connected via the sludge return pipe 44 via the sludge return pump 25. In the piping 36, a flow rate measuring device 19 is provided on the downstream side of the treated water supply pump 17 for measuring the flow rate of the treated water; on the downstream side of the flow rate measuring device 19, on the upstream side of the connection point of the sludge return piping 44, via The molybdenum compound supply pump 21 is connected to the molybdenum compound supply pipe 26. The piping 40 and the denitrification device 12 are connected by the nitrification liquid return piping 46.

In the water treatment device 5, the treated water containing ammonia nitrogen is fed to the denitrification device 12 through the piping 36 from the treated water adjustment tank 15 through the treated water supply pump 17 through the piping 36. On the other hand, from the nitrification device 10 in the latter stage, at least a part of the nitrification liquid is sent to the denitrification device 12 through the nitrification liquid return pipe 46. Here, in the piping 36, the molybdenum compound is supplied to the water to be treated by the molybdenum compound supply pump 21 through the molybdenum compound supply pump 21, so that the molybdenum compound is present so that the molybdenum concentration becomes 0.025 mgMo/gN or more (molybdenum compound supply step).

In the nitrification device 10, the ammonia nitrogen contained in the treated water is oxidized to nitrous acid or nitrate nitrogen by the nitrifying bacteria contained in the self-supporting ammonia oxidizing bacteria and nitrite oxidizing bacteria contained in the microbial activated sludge (Nitrification step). In the denitrification device 12, the nitrous acid or nitrate nitrogen produced in the nitrification device 10 (nitrification step) is reduced to nitrogen by the heterogeneous denitrification bacteria contained in the microorganism activated sludge (denitrification step) . The denitrification liquid is sent to the nitrification device 10 through the pipe 38; at least a part of the nitrification liquid is sent to the solid-liquid separation device 14 through the pipe 40. Thereafter, the treatment is performed in the same manner as the water treatment device 1 of FIG. 1.

To further reduce the nitrogen concentration of the treated water, a nitrification device 10 and a solid-liquid separation device 14 of the water treatment device 5 of FIG. 3 may be further provided with a post-nitrogen removal device, a post-nitrogen removal device, and an oxidation device Oxidation device.

An example of such a water treatment device is shown in FIG. 4. The water treatment device 7 of FIG. 4 is further provided with a denitrification device 48 as a post-denitrification device, and an oxidation device 30 as an oxidation device. The outlet of the nitrification device 10 and the inlet of the rear denitrification device 48 are connected by piping 50; the outlet of the rear denitrification device 48 and the inlet of the oxidation device 30 are connected by piping 52; the outlet of the oxidation device 30 is connected to The inlet of the solid-liquid separation device 14 is connected by a pipe 54. The rear nitrogen removal device 48 is connected to the hydrogen donor supply pipe 28 via the hydrogen donor supply pump 23. The piping 50 and the denitrification device 12 are connected by the nitrification liquid return piping 46.

In the water treatment device 7, the treated water containing ammonia nitrogen is fed to the denitrification device 12 through the piping 36 from the treated water adjustment tank 15 by the treated water supply pump 17 through the piping 36. On the other hand, from the nitrification device 10 in the latter stage, at least a part of the nitrification liquid is sent to the denitrification device 12 through the nitrification liquid return pipe 46. Here, in the piping 36, the molybdenum compound is supplied to the water to be treated by the molybdenum compound supply pump 21 through the molybdenum compound supply pump 21, so that the molybdenum compound is present so that the molybdenum concentration becomes 0.025 mgMo/gN or more (molybdenum compound supply step).

In the nitrification device 10, the ammonia nitrogen contained in the treated water is oxidized to nitrous acid or nitrate nitrogen by the nitrifying bacteria contained in the self-supporting ammonia oxidizing bacteria and nitrite oxidizing bacteria contained in the microbial activated sludge (Nitrification step). In the denitrification device 12, the nitrous acid or nitrate nitrogen produced in the nitrification device 10 (nitrification step) is reduced to nitrogen gas by the heterogeneous denitrification bacteria contained in the microbial activated sludge. The denitrification liquid is sent to the nitrification device 10 through the piping 38; at least a part of the nitrification liquid is sent to the rear denitrification device 48 through the piping 50; in the post-denitrification device 48, by denitrifying bacteria, the Nitrous acid or nitrate nitrogen produced by the nitrification unit 10 (nitrification step) is reduced to nitrogen (denitrification step). The nitrogen removal liquid is sent to the oxidation device 30 through the piping 52. Thereafter, the treatment is performed in the same manner as the water treatment device 3 of FIG. 2. At least a part of the nitrification liquid is sent to the denitrification device 12 through the nitrification liquid return pipe 46.

In the denitrification step, the amount of hydrogen donor added is given a time change so that the difference between the maximum concentration and the minimum concentration of the hydrogen donor in the hydraulic retention time of the treated water becomes 50 mgTOC/L or more. In this way, microbial activated sludge containing nitrifying bacteria and denitrifying bacteria is granulated. By varying the concentration of the hydrogen donor to be added in the denitrification reaction, it is possible to simply form the granules of denitrification bacteria self-granulation.

Further, by circulating these particles in the treatment system for nitrogen-containing water that performs nitrification and denitrification, all the bacteria such as nitrifying bacteria are granulated, and the entire treatment device for nitrogen-containing treated water can be Substantially the same particle treatment.

In addition, when the difference between the maximum concentration and the minimum concentration of the hydrogen donor in the denitrification step is increased to efficiently granulate the microbial activated sludge, the denitrification step can include at least the first denitrification step and More than 2 steps in the second nitrogen removal step. The denitrification step includes at least a first denitrification step and a second denitrification step; in the denitrification step, a hydrogen donor can be supplied at least in the first denitrification step to make the hydraulic power of the second denitrification step treated water The difference between the maximum concentration of the hydrogen donor in the first denitrification step and the minimum concentration of the hydrogen donor in the second denitrification step in the residence time becomes 50 mgTOC/L or more.

An example of such a water treatment device is shown in FIG. 5. The water treatment device 9 of FIG. 5 includes a first nitrogen removal device 58 and a second nitrogen removal device 60 as nitrogen removal means. The outlet of the nitrification device 10 and the inlet of the first denitrification device 58 are connected by a pipe 62; the outlet of the first denitrification device 58 and the inlet of the second denitrification device 60 are connected by a pipe 64; 2 The outlet of the denitrification device 60 and the inlet of the oxidation device 30 are connected by a pipe 66.

The nitrification liquid obtained in the nitrification device 10 is sent to the first denitrification device 58 through the pipe 62. In the first denitrification device 58, the hydrogen donor is supplied through the hydrogen donor supply pump 23, and the hydrogen donor is supplied through the hydrogen donor supply pipe 28. After contacting with the denitrifying bacteria contained in the microorganism activated sludge, they are mixed. The liquid is sent to the second denitrification device 60 through the piping 64. In the second denitrification device 60, the nitrite or nitrate nitrogen generated in the nitrification device 10 (nitrification step) is reduced to nitrogen by the denitrifying bacteria (Denitrification step). The nitrogen removal liquid is sent to the oxidation device 30 through the piping 66. Thereafter, the treatment is performed in the same manner as the water treatment device 3 of FIG. 2.

In the water treatment device 1 of FIG. 1, an ammonia nitrogen concentration measuring device for measuring the concentration of ammonia nitrogen can be installed in the water treatment tank and the water treatment tank to measure the ammonia nitrogen concentration of the water to be treated and the water to be treated.

An example of these forms of water treatment equipment is shown in FIG. 6. The water treatment device 2 of FIG. 6 may include a treatment water tank 67 for storing treatment water, and a pipe 22 is connected to the inlet of the treatment water tank 67. Ammonia nitrogen concentration measuring devices 63 and 65 as measuring means for ammonium nitrogen concentration are provided in the treated water adjustment tank 15 and the treated water tank 67, respectively. The ammonia nitrogen concentration measuring device 65 may be installed in the nitrification device 10 instead of the treatment water tank 67. With this, the processing amount of the nitrification device 10 can be grasped.

The ammonia nitrogen concentration of the treated water is measured by the ammonia nitrogen concentration measuring device 63, the ammonia nitrogen concentration of the treated water is measured by the ammonia nitrogen concentration measuring device 65, the sludge concentration in the nitrification device 10 is measured, and the treated water is adjusted The flow rate of the supply pump 17 may be set to a predetermined processing rate per unit of sludge. In addition, the molybdenum compound supply pump 21 may control the amount of molybdenum added with respect to the amount of nitrogen flowing in. In this case, the treated water supply pump 17, the flow rate measuring device 19, the molybdenum compound supply pump 21, and the ammonia nitrogen concentration measuring devices 63 and 65 function as a nitrification speed control means for performing the following control: in the nitrification device 10 In the treatment of water, molybdenum compounds are present so that the molybdenum concentration becomes 0.025 mgMo/gN or more, and the nitrification rate per unit sludge becomes 0.11 [kgN/(kgVSS·day)] or more. With this configuration, it is possible to track changes in the concentration of the water to be treated. The treated water supply pump 17, the flow rate measuring device 19, the molybdenum compound supply pump 21, and the ammonia nitrogen concentration measuring devices 63, 65 can be connected to the control device by electrical connection or the like to perform automatic control.

In the water treatment device 1 of FIG. 1, the carrier can be used in the nitrification device and the nitrogen removal device.

An example of these forms of water treatment equipment is shown in FIG. 7. In the water treatment device 4 of FIG. 7, in the nitrification device 10, the carrier 68 is held in the water tank; in the denitrification device 12, the carrier 70 is held in the water tank; and at the outflow of each water tank, suppression carriers 68, 70 are provided的出之之网72,74.

The measurement of the amount of sludge in the nitrification device 10 is calculated from the measurement of the amount of sludge in the float and the filling amount of the carrier. The amount of sludge attached to each unit of carrier is almost constant, so it can be measured by measuring the amount of sludge attached to each unit of carrier in advance.

In the water treatment device 4 of FIG. 7, a solid-liquid separation device may not be provided, so that the sludge return is not performed.

An example of such a water treatment device is shown in FIG. 8. The water treatment device 6 of FIG. 8 is provided with an oxidation device 30 in the rear stage of the denitrification device 12. In the oxidation device 30, the carrier 76 is held in the water tank; at the outlet of the water tank, a screen 78 for suppressing the outflow of the carrier 76 is provided.

In the water treatment device 6 of FIG. 8, the outlet of the denitrification device 12 and the inlet of the oxidation device 30 are connected by a pipe 80; the pipe 82 is connected to the outlet of the treated water of the oxidation device 30.

The denitrification liquid obtained in the denitrification device 12 (denitrification step) is sent to the oxidation device 30 through the pipe 80. In the oxidation step in the oxidation device 30, the hydrogen donor is treated in an aerobic manner in an oxidation section (for example, an oxidation tank). The oxidizing section (for example, an oxidizing tank) is connected to the air introduction pipe in the same manner as the nitrification section, for example, and has a structure that can supply oxygen-containing gas such as air to the water to be treated in the oxidizing section.

Although there is a possibility that a hydrogen donor is added to the denitrification device 12 and the hydrogen donor remains after the denitrification treatment, the quality of the treated water deteriorates. However, in the oxidation device 30, the hydrogen donor is treated in an aerobic manner. [Example]

Hereinafter, examples and comparative examples will be listed to explain the present invention more specifically and in detail, but the present invention is not limited to the following examples.

The following shows examples and comparative examples using a continuous water flow tester. In addition, it was implemented under the conditions of all controlled at room temperature of 20°C.

<Example 1> In Example 1, the laboratory scale test machine of the structure of the water treatment apparatus 9 shown in FIG. 5 was used. The nitrifying bacteria and denitrifying bacteria are granulated, and the nitrifying and denitrifying treatment test of simulated drainage is carried out. As the simulated drainage, a solution in which 400 mg N/L of ammoniacal nitrogen is dissolved in pure water and phosphoric acid and trace element chemicals are added as other nutrient sources is used. The trace element liquid used in this test uses a liquid that does not contain molybdenum. The hydrogen supply system used for denitrification uses methanol, which is added discontinuously to the first denitrification tank, so that the difference between the maximum methanol concentration in the first denitrification tank and the minimum methanol concentration in the second denitrification tank , Becomes 50mgTOC/L or more. A pH controller is installed in the nitrification tank, the first denitrification tank, and the second denitrification tank, and the pH in the tank is adjusted to 7 to 7.5 using hydrochloric acid or sodium hydroxide. The concentrated sludge obtained from the solid-liquid separation tank is returned to the nitrification tank. From day 0 to day 45, molybdenum was not added (Comparative Example 1), and from day 46, a molybdenum compound (sodium molybdate) was added to the treated water to make it 0.1 mgMo/L (Example 1) ). The condition for the addition concentration of molybdenum is that the nitrogen concentration with respect to the water to be treated is 0.25 mgMo/gN. The results are shown in Figures 9 and 10. Fig. 9 shows the change of the nitrification tank volume load [kgN/(m ³ ·day)] and the nitrification tank's ammonia nitrogen concentration [mgN/L]; Fig. 10 shows the denitrification tank relative to the number of days passed [day] Changes in volumetric load [kgN/(m ³ ·day)] and total nitrogen concentration of treated water [mgN/L]

In the first comparative example 1, the volume load in the nitrification tank was 0.2 kgN/(m ³ ·day), but water flow was started, but the ammonia nitrogen in the nitrification tank remained 5-60 mgN/L, and the load could not be increased, and the nitrification rate Stay at 0.15～0.25kgN/(m ³ ·day). As the nitrification rate stays, the nitrogen removal rate also stays at 0.3 to 0.5 kgN/(m ³ ·day). In the period of Comparative Example 1, the treatment rate per unit of sludge that could be stably operated was 0.05kgN/(kgVSS·day) at the nitrification rate.

Next, after the addition of molybdenum to the water to be treated was started, the treatment rate was found to increase, and a nitrification rate of 1.1 kgN/(m ³ ·day) was confirmed at the maximum. In addition, during the period of Example 1, the ammonia nitrogen in the nitrification tank always shifted below 1 mgN/L. Along with the increase in the nitrification rate, it was also found that the denitrification rate increased to a maximum of 2.2 kgN/(m ³ ·day). During the period of Comparative Example 1, it was confirmed that the treatment rate per unit of sludge indicating sludge activity was stable at a nitrification rate of 0.24 kgN/(kgVSS·day) and a nitrogen removal rate of 0.54 kgN/(kgVSS·day).

<Comparative example 2> In Comparative Example 2, a continuous water-passing test was performed using a laboratory-scale testing machine composed of the water treatment device 9 shown in FIG. 5. As the simulated drainage, an adjustment is made so that the ammonia nitrogen in pure water becomes 800 mgN/L, and other chemical solutions (excluding molybdenum) added with phosphoric acid and trace elements. For the purpose of replenishing trace elements, the well water without molybdenum (molybdenum concentration: 0.0001mgMo/L (below detection limit)) is added to the 10% flow rate of the treated water from the 120th to the 215th, from the 216th From day to day 280, add 10% of the treated water containing molybdenum industrial water to the treated water for replenishment. In addition, the concentration of molybdenum in industrial water is 0.0006 mgMo/L. The concentration of molybdenum in well water and industrial water is measured by ICP mass analysis (ICP-MS).

Figure 11 shows the transition of the nitrification tank volume load [kgN/(m ³ ·day)] and the residual ammoniacal nitrogen concentration of the nitrification tank [mgN/L], and Figure 12 shows the denitrification tank volume load [kgN/(m ³・Day)] Change with total nitrogen concentration [mgN/L] of treated water. As can be seen from FIG. 11, although the volume load of the nitrification tank increased to 0.8 kgN/(m ³ ·day), the ammonia nitrogen concentration remained 41 mgN/L on the 169th day, and rose to 130 mgN/L on the 171st day. After that, the nitrification performance was also unstable, and 10 to 40 mgN/L remained in the nitrification tank, which made it impossible to operate stably. In addition, the nitrification activity during the test period was 0.02 to 0.075 kgN/(kgVSS·day). Along with the instability of nitrification, the denitrification treatment is also unstable, and the TN of the treated water rises to a maximum of 150 mgN/L.

<Example 2> Using the simulated drainage and test device with the same conditions as in Comparative Example 2, the effect of addition of the molybdenum compound solution was verified by continuous water flow test. The addition concentration of molybdenum was 0.02 mgMo/L with respect to the ammonia nitrogen concentration of the treated water of 800 mgN/L, and the addition was started from the 175th day. The condition for the addition concentration of molybdenum is that the nitrogen concentration with respect to the water to be treated is 0.025 mgMo/gN.

Figure 13 shows the transition of the nitrification tank volume load [kgN/(m ³ ·day)] and the residual nitrification nitrogen concentration of the nitrification tank [mgN/L], and Figure 14 shows the denitrification tank volume load [kgN/(m ³・Day)] Change with total nitrogen concentration [mgN/L] of treated water. As a result, during the period when no molybdenum was added, the volume load of the nitrification tank did not increase, and ammonia nitrogen remained at 55 mgN/L on the 175th day. After adding the Mo compound from the 175th day, it was confirmed that the ammonia nitrogen concentration had decreased, and even if the volume load was increased to 0.8 to 0.9 kgN/(m ³ ·day), stable operation was possible. The maximum nitrification activity before molybdenum addition was 0.05 kgN/(kgVSS·day), but the nitrification activity after the start of molybdenum addition increased to 0.11 kgN/(kgVSS·day). Regarding denitrification, the volume load of the denitrification tank also increased to 1.4 kgN/(m ³ ·day).

<Example 3> The simulated drainage and test device with the same conditions as in Example 2 were used to verify the effect of the addition of molybdenum compound by continuous water flow test. The addition concentration of molybdenum was 0.1 mgMo/L with respect to the ammonia nitrogen concentration of the treated water at 800 mgN/L, and the addition began on the 343rd day. The condition for the addition concentration of molybdenum is that the nitrogen concentration with respect to the water to be treated is 0.125 mgMo/gN.

Figure 15 shows the transition of the nitrification tank volume load [kgN/(m ³ ·day)] and the residual nitrification nitrogen concentration of the nitrification tank [mgN/L], and Figure 16 shows the denitrification tank volume load [kgN/(m ³・Day)] Change with total nitrogen concentration [mgN/L] of treated water. As a result, during the period when no molybdenum was added, nitrate nitrogen of about 70 to 80 mg/L was detected in the denitrification tank, so the load could not be increased, and the volume load of the nitrification tank stayed at about 0.25 kgN/(m ³ ·day). Starting from day 343, the addition of molybdenum solution was attempted to increase the load. On the 346th day, ammonia nitrogen was detected at 37mgN/L in the nitrification tank, but the ammonia nitrogen concentration was found to decrease thereafter. The volume load of the nitrification tank was increased to 0.86 kgN/(m ³ ·day), but ammonia nitrogen was not detected in the nitrification tank, and the treated water TN in the denitrification tank also shifted below 5 mgN/L. The nitrification activity before the addition of molybdenum remained at 0.05 to 0.06 kgN/(kgVSS·day), but after the start of the addition of molybdenum, an improvement in activity was found, and an increase to 0.2 kgN/(kgVSS·day) was confirmed.

A summary of the above results is shown in Figure 17. From FIG. 17, it is understood that in the nitrification step, the molybdenum compound is preferably present in the water to be treated so that the molybdenum concentration becomes 0.025 mgMo/gN or more.

In this way, by the method of the embodiment, in the biological treatment of the treated water containing ammoniacal nitrogen, even if the nitrogen concentration in the treated water is high, it can still be treated stably at a rapid treatment rate.

Hereinafter, the influence of the added concentration of the molybdenum compound on the ammonia oxidation reaction and the denitrification reaction will be evaluated by batch testing.

[Test of the effect of addition of molybdenum on denitrification (batch test)] Using nitrification denitrification sludge, the effect of the addition of molybdenum on the denitrification reaction was verified by batch testing using simulated drainage. The specific method of the experimental method is as follows.

1. As the simulated drainage used for batch testing, use nitrate ion in well water to make it 60mgN/L, and add phosphoric acid phosphate to make it 1mgP/L. In addition, the concentration of molybdenum in the simulated drainage is 0.0001 mg/L or less. 2. The sludge previously acclimated with methanol as a hydrogen donor is washed with pure water, suspended in simulated drainage, and dispensed into 5 beakers. 3. Add the sodium molybdenum solution to each beaker of the mixed liquid of sludge and simulated drainage to make it equal to 0mgMo/L, 1mgMo/L, 5mgMo/L, 10mgMo/L, 20mgMo/L and stir. 4. Stir, and add the same amount of methanol as hydrogen donor to each beaker one by one to evaluate the reduction rate of nitric acid.

As a result of the denitrification activity test, the denitrification activity calculated from the reduction rate of nitric acid and the amount of sludge in the beaker became 0.43gN/gSS/day for the series without added Mo, and 0.46gN/day for the series with Mo concentration of 1mgMo/L gSS/day becomes 0.45gN/gSS/day in the 5mgMo/L series, 0.42gN/gSS/day in the 10mgMo/L series, and 0.41gN/gSS/day in the 20mgMo/L series, with no added Mo Although the series is relatively small, an 8% activity improvement was confirmed in the series with a Mo concentration of 1 mgMo/L, and a 5% activity improvement was confirmed in the series with 5 mgMo/L. On the other hand, in the series with a high concentration of Mo added to 20 mgMo/L, compared with the series with a concentration of 1 mgMo/L with the highest denitrification activity, only about 10% activity reduction was confirmed, not confirmed. Mo obviously hinders denitrification.

[Test of the effect of Mo addition on ammonia oxidation (batch test)] Using nitrification denitrification sludge, the effect of the addition of molybdenum on the ammonia oxidation reaction was verified by batch testing using simulated drainage. The specific method of the experimental method is as follows.

1. As the simulated drainage used in batch testing, use ammonia ion in the well water to make it 60mgN/L, and add phosphorous phosphate to make it 1mgP/L. In addition, the concentration of molybdenum in the simulated drainage is 0.0001 mg/L or less. 2. Suspend the test sludge washed with pure water in the simulated drainage and dispense it into 5 beakers. 3. In the mixed liquid of sludge and simulated drainage, add sodium molybdate solution to each beaker to make it become 0mgMo/L, 0.1mgMo/L, 0.5mgMo/L, 2mgMo/L, 10mgMo/L, and start aeration respectively . 4. Evaluate the reduction rate of each ammonia nitrogen concentration.

As a result of the ammonia oxidation activity test, the ammonia oxidation activity calculated from the ammonia reduction rate and the amount of sludge in the beaker becomes 0.18gN/gSS/day for the series without added Mo, and becomes 0.13gN for the series with Mo concentration of 0.1mgMo/L /gSS/day, it becomes 0.13gN/gSS/day in the 0.5mgMo/L series, 0.13gN/gSS/day in the 2mgMo/L series, and 0.10gN/gSS/day in the 10mgMo/L series. The series with Mo added had the highest ammonia oxidation activity, and the series with 10 mgMo/L had the lowest ammonia oxidation activity. From the test results of this batch, it was found that in order to suppress the hindrance of the molybdenum concentration on the ammonia oxidation reaction, it should be made 2 mgMo/L or less.

1, 2, 3, 4, 5, 6, 7, 9: water treatment device 10: Nitrification device 12: Denitrification device 14: Solid-liquid separation device 15: Adjusted tank for treated water 16, 18, 20, 22, 32, 34, 36, 38, 40, 42, 50, 52, 54, 62, 64, 66, 80, 82: piping 17: Processed water supply pump 19: Flow measuring device 21: Molybdenum compound supply pump 23: Hydrogen donor supply pump 24, 44: Sludge return piping 25: Sludge return pump 26: Molybdenum compound supply piping 28: Hydrogen donor supply piping 30: Oxidation device 46: Nitrification liquid return piping 48: After denitrification device 58: The first nitrogen removal device 60: Second nitrogen removal device 63, 65: Ammonia nitrogen concentration measuring device 67: Treatment sink 68, 70, 76: carrier 72, 74, 78: screen mesh

FIG. 1 is a schematic configuration diagram showing an example of a water treatment device according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing another example of the water treatment device according to the embodiment of the present invention. Fig. 3 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention. Fig. 4 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention. Fig. 5 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention. Fig. 6 is a schematic configuration diagram showing another example of the water treatment device according to the embodiment of the present invention. 7 is a schematic configuration diagram showing another example of the water treatment device according to the embodiment of the present invention. Fig. 8 is a schematic configuration diagram showing another example of the water treatment device according to the embodiment of the present invention. 9 is a graph showing the volume load of the nitrification tank [kgN/(m ³ ·day)] and the ammonia nitrogen concentration of the nitrification tank [mgN/L] in Example 1 and Comparative Example 1 with respect to the number of days passed [day] chart. Fig. 10 shows the volume load of the denitrification tank [kgN/(m ³ ·day)] and the total nitrogen concentration [mgN/L] of the treated water in Example 1 and Comparative Example 1 with respect to the number of days passed [day] chart. FIG. 11 is a graph showing the volume load of the nitrification tank [kgN/(m ³ ·day)] and the ammonia nitrogen concentration of the nitrification tank [mgN/L] in Comparative Example 2 with respect to the number of days passed [day]. FIG. 12 is a graph showing the volume load of the denitrification tank [kgN/(m ³ ·day)] and the total nitrogen concentration of the treated water [mgN/L] in Comparative Example 2 with respect to the number of days passed [day]. 13 is a graph showing the volumetric load of the nitrification tank [kgN/(m ³ ·day)] and the ammonia nitrogen concentration of the nitrification tank [mgN/L] in Example 2 with respect to the number of days passed [day]. 14 is a graph showing the volume load [kgN/(m ³ ·day)] of the denitrification tank and the total nitrogen concentration [mgN/L] of the treated water in Example 2 with respect to the number of days passed [day]. 15 is a graph showing the volumetric load of the nitrification tank [kgN/(m ³ ·day)] and the ammonia nitrogen concentration of the nitrification tank [mgN/L] in Example 3 with respect to the number of days passed [day]. 16 is a graph showing the volume load of the denitrification tank [kgN/(m ³ ·day)] and the total nitrogen concentration of the treated water [mgN/L] in Example 3 with respect to the number of days passed [day]. Fig. 17 is a graph showing the nitrification rate [kgN/(kgVSS·day)] relative to the molybdenum concentration (Mo/N [mg/g]) in Examples.

1: Water treatment device

10: Nitrification device

12: Denitrification device

14: Solid-liquid separation device

15: Adjusted tank for treated water

16, 18, 20, 22: piping

17: Processed water supply pump

19: Flow measuring device

21: Molybdenum compound supply pump

23: Hydrogen donor supply pump

24: Sludge return piping

25: Sludge return pump

26: Molybdenum compound supply piping

28: Hydrogen donor supply piping

Claims (13)

A water treatment method that treats the treated water containing ammonia nitrogen biologically; Including nitrification step: oxidize the ammoniacal nitrogen to nitrous acid or nitrate nitrogen by the nitrifying bacteria contained in the self-supporting ammonia oxidizing bacteria and nitrite oxidizing bacteria contained in the microbial activated sludge; It is characterized by: In the nitrification step, the molybdenum compound is present in such a way that the molybdenum concentration relative to the water to be treated becomes 0.025 mgMo/gN or more; The nitrification rate per unit of sludge is above 0.11 [kgN/(kgVSS·day)]. For example, the water treatment method according to item 1 of the patent scope, in which The molybdenum concentration in the nitrification step is 2 mgMo/L or less with respect to the water to be treated. For example, the water treatment method according to item 1 or 2 of the patent scope, in which The nitrogen concentration in the water to be treated is 100 mgN/L or more. For example, the water treatment method according to item 1 or 2 of the patent scope, in which It also includes a denitrification step, which reduces the nitrous acid or nitrate nitrogen produced in the nitrification step to nitrogen by the denitrifying bacteria contained in the microbial activated sludge. For example, the water treatment method in item 4 of the patent application scope, in which In the denitrification step, the amount of addition of the hydrogen donor is given a time change so that the difference between the maximum concentration and the minimum concentration of the hydrogen donor in the hydraulic retention time of the treated water becomes 50 mgTOC/L or more, so as to include The microbial activated sludge of the nitrifying bacteria and denitrifying bacteria is granulated. For example, the water treatment method in item 5 of the patent application scope, in which The nitrogen removal step includes at least a first nitrogen removal step and a second nitrogen removal step; In the denitrification step, the hydrogen donor is supplied at least in the first denitrification step so as to maximize the hydrogen donor of the first denitrification step in the hydraulic residence time of the treated water in the second denitrification step The difference between the concentration and the minimum concentration of the hydrogen donor in the second denitrification step becomes 50 mgTOC/L or more. A water treatment device that biologically treats water to be treated that contains ammoniacal nitrogen includes: Nitrification means by oxidizing the ammoniacal nitrogen to nitrous acid or nitrate nitrogen by the nitrifying bacteria contained in the self-supporting ammonia oxidizing bacteria and nitrite oxidizing bacteria contained in the microbial activated sludge; and The nitrification rate control means performs the following control: in this nitrification means, the molybdenum compound is present so that the molybdenum concentration with respect to the water to be treated becomes 0.025 mgMo/gN or more, and the nitrification rate per unit sludge becomes 0.11 [kgN/(kgVSS·day)] or more. For example, the water treatment device of item 7 of the patent application scope, in which The nitrification rate control means controls the molybdenum concentration in the nitrification means to be 2 mgMo/L or less with respect to the water to be treated. For example, the water treatment device of patent application item 7 or 8, wherein, The concentration of molybdenum in the water to be treated is 0.0001 mgMo/L or less. For example, the water treatment device of patent application item 7 or 8, wherein, The nitrogen concentration in the water to be treated is 100 mgN/L or more. For example, the water treatment device of patent application item 10, where, It also includes a denitrification means that reduces the nitrous acid or nitrate nitrogen produced by the nitrification means to nitrogen by the denitrification bacteria contained in the microbial activated sludge. For example, the water treatment device according to item 11 of the patent scope, in which It further includes a hydrogen donor concentration control means, which performs the following control: in the denitrification means, the amount of addition of the hydrogen donor is given a time change so that the maximum concentration of the hydrogen donor in the hydraulic retention time of the treated water The difference from the minimum concentration becomes 50 mgTOC/L or more, whereby the microbial activated sludge containing the nitrifying bacteria and denitrifying bacteria is granulated. For example, the water treatment device according to item 12 of the patent scope, in which The nitrogen removal means includes at least a first nitrogen removal means and a second nitrogen removal means; The hydrogen donor concentration control means performs the following control: in the denitrification means, a hydrogen donor is supplied at least in the first denitrification means, so that the hydraulic retention time of the treated water in the second denitrification means The difference between the maximum concentration of the hydrogen donor of the first denitrification means and the minimum concentration of the hydrogen donor of the second denitrification means becomes 50 mgTOC/L or more.

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